The structure and function of intermediate filaments (IF) will be investigated in a variety of cultured epithelial cells and fibroblasts. In the fibroblast IF system, the major structural proteins have been defined and, therefore, this research will concentrate on two classes of IF-associated proteins (IFAPs), one of 60-70K molecular weight and one of 250-350K molecular weight. In epithelial cells, our efforts will focus on elucidating the function and biochemical properties of IF bundles and their interactions with desmosomes and the nuclear envelope. The possibility that multiple IF systems exist in a single cell will also be investigated using a biochemical approach. Other studies will focus on the possible interactions between the centrosomes and IF, the isolation of centrosomes and alterations in IF in transformed cells. The cell types to be used in these studies include BHK-21, HeLa, PtKl, mouse epidermal keratinocytes, transformed mouse epidermal cells and virus-transformed mouse and hamster cells. A multifaceted approach will be taken in all studies and techniques will include the isolation and biochemical-biophysical characterization of IF, in vitro polymerization assays, the use of monoclonal and polyclonal antibodies, immunofluorescence and other light optical methods and all aspects of electron microscopy.